The thermodynamic effects of exposing nucleic acid bases to water: Solubility measurements in water and organic solvents

Abstract

Abstract In order to examine the thermodynamic effects of exposing nucleic acid bases to water, we have measured the solubility of adenine, cytosine, and uracil in water and in organic solvents as a function of temperature. Transfer of a nucleic acid base from an organic environment into water is characterized by positive values for Δ H and for Δ S . We conclude from this result that the overall interaction between nucleic acid bases and water cannot be hydrophobic. If the effect we observe represents structure breaking in water by nucleic acid bases, this process would account for a major portion of the large, positive melting entropy of DNA, and would also contribute substantially to the melting enthalpy.